Friction stir bonding method

ABSTRACT

When stacking a plate  20  on a plate  10,  the stacked surface of the plate  10  is provided with a groove  12.  The outer portion of the other plate  20  is equipped with a convex portion  22.  A rotary tool  50  is inserted from the convex portion  22  in performing a friction stir bonding. Said groove  12  is filled up during the friction stir bonding by the metal material constituting said convex portion  22.  According to the present method, the pressure of said bonding portion will not be excessive, and therefore prevents the generation of a notch to the stacked surface. The present invention provides a friction stir bonding method realizing a lightweight joint having good characteristics.

FIELD OF THE INVENTION

[0001] The present invention relates to a method for friction stir bonding stacked surfaces.

DESCRIPTION OF THE RELATED ART

[0002] A friction stir bonding method is a method for bonding member by inserting a round shaft (called a rotary tool) to a joint portion, moving the tool along the joint line, thereby heating, mobilizing and plasticising the joint portion in order to perform solid-phase bonding of the members. The rotary tool comprises a large-diameter portion and a small-diameter portion. The small-diameter portion is to be inserted to the members to be bonded, and the end surface of the large-diameter portion contacts the members. The small-diameter portion is equipped with a screw.

[0003] Moreover, a convex portion is formed to the side the rotary tool is to be inserted of the two members to be bonded, the metal material that forms the convex portion mobilized to fill the gap between the two members. The large-diameter portion of the rotary tool is arranged to fit in the convex portion.

[0004] These methods are disclosed in Japanese Patent Laid-Open Publication No. 11-90655 (U.S. Pat. No. 6,050,474).

SUMMARY OF THE INVENTION

[0005] Friction stir bonding can be applied for joining stacked (superposed) surfaces. When the stacked members are bonded through friction stir bonding, a notch is formed on the stacked surfaces. An example is shown in FIG. 4. FIG. 4(A) is a vertical cross-sectional view showing the midst of friction stir bonding, and FIG. 4(B) is a vertical cross-sectional view showing the state after the friction stir bonding. FIG. 4(B) is a simplified explanatory view. The friction stir bonding is performed by inserting a rotary tool 50 to the stacked members from the upper direction. The stirred region shown by the hatching and the stacked surface of the two members constitute a notch B knuckled to the upper side.

[0006] The object of the present invention is to provide a friction stir bonding method capable of preventing the generation of notches to the stacked surfaces.

[0007] The present invention characterizes in stacking a first member and a second member, providing a groove on the stacked surface of the first member along the direction of friction stir bonding, and performing friction stir bonding to the stacked surfaces along the groove using a rotary tool having a small-diameter portion with a diameter greater than the width of the groove.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a vertical cross-sectional view showing the joint portion according to one embodiment of the present invention;

[0009]FIG. 2 is a vertical cross-sectional view showing the midst of bonding of FIG. 1;

[0010]FIG. 3 is a vertical cross-sectional view showing the state after the friction stir bonding of FIG. 1; and

[0011]FIG. 4 is a vertical cross-sectional view showing the prior-art bonding method.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0012] One preferred embodiment of the present invention will now be explained with reference to FIGS. 1 through 3. FIG. 3 shows a simplified view of the stirred region in hatching. A plate 20 is stacked on a plate 10. The stacked area of the plate 10 (the upper surface) is provided with a substantially square-shaped groove 12. A convex portion 22 is provided to the upper surface of the plate 20. The plate 10 is mounted on a stage 100, and is fixed on the stage 100 together with the plate 20. The plates 10 and 20 are protruded members.

[0013] Friction stir bonding is performed by inserting a rotary tool 50 from the upper direction of the upper plate 20. The rotary tool 50 includes a large-diameter portion 51 and a small-diameter portion 52 formed on the end of said large-diameter portion. A screw is mounted to the small-diameter portion 52. The center of the rotary tool 50 is inserted to the center of width of the convex portion 22. The center of the groove 12 is also located at said center. The diameter of the large-diameter portion 51 is smaller than the width of the convex portion 22. The width of the groove 12 is smaller than the diameter of the small-diameter portion 52 or the large-diameter portion 51.

[0014] Upon friction stir bonding, the lower end of the large-diameter portion 51 is positioned between the line extended from the surface of the plate 20 having the convex portion and the peak of the convex portion 22. The tip of the small-diameter portion 52 is inserted deeper than the bottom of the groove 12. In this state, the rotary tool 50 is rotated and moved along the line to be bonded. The axial core of the rotary tool 50 is set so that the small-diameter portion 62 side is positioned forward than the large-diameter portion 51 side in the direction of movement of the tool.

[0015] According to the present invention, the existence of the space formed by the groove 12 prevents the pressure of the stirred region from being excessive, and prevents the generation of a notch B.

[0016] Moreover, the groove 12 is filled up during the stir. The metal material constituting the convex portion 22 is plasticised and fills the groove 12. If the convex portion 22 does not exist, the upper surface of the plate 20 is scraped and the plate becomes thin, but since the present embodiment is equipped with a convex portion 22, the scraped portion is compensated by the convex portion 22, enabling, as a result, to reduce the plate thickness of the plate 20 as a whole.

[0017] The technical scope of the present invention is not limited to the terms used in the claims or in the summary of the present invention, but is extended to the range in which a person skilled in the art could easily substitute based on the present disclosure.

[0018] According to the friction stir bonding method of the present invention, a lightweight joint having good characteristics is achieved. 

We claim:
 1. A friction stir bonding method comprising the steps of: stacking a first member and a second member, the stacked surface of said first member having a groove formed along the direction in which the friction stir bonding is to be performed; and friction stir bonding said stacked surface along said groove using a rotary tool including a small-diameter portion having a diameter greater than the width of said groove.
 2. A friction stir bonding method according to claim 1, wherein said friction stir bonding is performed by inserting said small-diameter portion from said second member to a depth deeper than the depth of said groove.
 3. An extruded member used for friction stir bonding, including a surface to be stacked by another member, said surface being the surface to be friction-stir-bonded to said another member, having a groove along the direction of extrusion. 